I had the same problem and read here and some other places hours of solutions that part of the worked and part didn't.
Eventually I tried something simple and it worked for me:
1- Go to the WI-FI icon (up at the menu bar, at the top of the screen) (-I am assuming that you don't know where it is, if you do, just go to 2- there is a triangle with bars and rounded edge. This is the WIFI icon).
2- Click on it and then disable the WIFI connection (click on "Turn WI-FI off").
3- Wait some seconds and turn it on again.
4- My iPod appears in the iTunes side bar now.
That's all I do and, as I said, it works for me.
Hope it will work for you too.